1. OVERVIEW OF CLARA MODEL IMPROVEMENT TESTING Kenneth Kuhn – RAND Corporation Jordan Fischbach – RAND Corporation David Johnson – Purdue University

2. Overview of the Coastal Louisiana Risk Assessment (CLARA) Model 2

3. CLARA Model Estimates Direct Economic Damage from Coastal Flooding 3 Estimates flood depths across the coastDetermines direct economic damage Builds on post-Katrina flood modeling in coastal Louisiana Provides balanced resolution for future risk estimates – Estimates damage reduction from structural and nonstructural projects – Considers many future scenarios

4. CLARA Consists of Three Primary Modules 4 1. Statistical Pre-Processing Module 2. Flood Depth Module 3. Economic Damage Module

5. Summary of Modified JPM-OS Process 5

6. Response Surface Model Predicts Surge and Wave Response as a Function of Storm Parameters 6 Central pressure Radius Track Landfall angle Forward velocity Storms are parameterized by a set of characteristics 6 Surge and wave effects from training storms (ADCIRC/UnSWAN) Response surface estimation Surge and wave effects from “synthetic” storms

7. CLARA Estimates Flooding for Unenclosed and Enclosed Areas Enclosed protection system –Storm surge overtopping –Wave overtopping –Rainfall –Protection system breach 7 Unenclosed surge barrier – Storm surge overtopping – Storm surge “run-around” No levee protection –Storm surge –Wave heights

8. CLARA Fragility Module Considers the Possibility That Enclosed Protection Systems Might Fail Uses peak surge height and overtopping rates to estimate failure probability by location – Underseepage – Erosion (overtopping) Applies Monte Carlo simulation to probabilistically estimate failure rate Estimates breach flow volumes in the event of a failure 8 Example Fragility Curve

9. Approach based on FEMA HAZUS a.Project assets at risk b.Estimate monetary damage from floods of a given depth c.Calculate damage using modeled flood depth CLARA Determines Direct Economic Damage to Physical Assets Assets at risk $ Calculations performed for each grid point a) Monetary losses Flood depth $ c) 9 Damage by flood depth $ b) 9

10. Improvements for the 2017 Coastal Master Plan Analysis 10

11. Model Domain Expanded to Account for a Growing Floodplain and Support New Analysis 11 CLARA 2017 max extent

12. Developed a New Spatial Grid to Support Higher Resolution Analysis for Coastal Communities New grid provides at least 1 km resolution – 1 km grid for low-population areas, or – 2010 census block centroids for more dense areas LandScan population distribution data (~100 m) used to convert from census block populations to grid – Nighttime population ~ residential assets – Daytime population ~ commercial and industrial assets Key assumption: Assets at risk proportional to Landscan population within census blocks 12

13. 2012 version included approx. 35,000 census block centroids Developed a New Spatial Grid to Support Higher Resolution Analysis for Coastal Communities 13 2000 US Census block centroids

14. 2017 model includes approx. 114,000 grid points (90,000 in Louisiana) CLARA 2017 grid points 14 Developed a New Spatial Grid to Support Higher Resolution Analysis for Coastal Communities

15. Updated and Improved Database of Assets at Risk Added new critical infrastructure classes Replaced or augmented existing assets with new information 2010 Census Tax parcel data (source: recent Corps of Engineers investigations) 15

16. Incorporated Parametric Uncertainty into Flood Depth Estimates Using Several Methods 16 Flood depths in unenclosed areas – Random error in ADCIRC/UnSWAN – Uncertainty in the response surface fits – Random error in ground elevation estimates Flood depths in enclosed areas – Uncertainty in the response surface fits on the boundary of the protection system – Surge and wave overtopping rates (van der Meer) Uncertainty in the relative probabilities of each synthetic storm Monte Carlo Simulation Bootstrap Resampling

17. Scenario Uncertainty Approach and Methods Updated for 2017 Levee erosion and failure 2012: Used Interagency Performance Evaluation Taskforce (IPET) approach 2017: Incorporated multiple Corps of Engineers methods for estimating erosion failure as scenarios Future 50-year population and asset growth 2012: Simple coastwide population growth and urban/rural distribution assumptions 2017: Revised approach that considers physical changes over time (flood depth, land loss) 17

18. THANK YOU Kenneth Kuhn| kkuhn@rand.org